1. Field of the Invention
The present invention relates to a two-cycle internal combustion engine configured to prevent blow-by of an air-fuel mixture in a combustion engine for enhancing the combustion stability, fuel consumption, and exhaust gas purifying performance. In particular, the present invention is directed to a two-cycle internal combustion engine in which a chamber portion is disposed adjacent to a combustion chamber, a communication passage is provided between the combustion chamber and the chamber portion, and a control valve for openably/closably controlling the communication passage is disposed in the communication passage, wherein fuel or an air-fuel mixture is supplied into the combustion chamber via the communication passage.
2. Description of Background Art
In conventional two-cycle internal combustion engines, a blow-by phenomenon often occurs, wherein an air-fuel mixture supplied into the combustion chamber via the crank chamber is discharged through the exhaust passage. To solve such a problem, the present applicant has disclosed a two-cycle internal combustion engine in Japanese Patent Laid-open No. Hei 10-325323.
FIG. 12 of the present invention is a longitudinal sectional view of the internal combustion engine disclosed in the above-described document, and FIG. 13 is a horizontal sectional view cut along a cross-sectional plane passing through the rotary valve shown in FIG. 12. Referring to these figures, a communication passage for communicating a combustion chamber 013 to a chamber portion 029 is provided in a cylinder block 003, and a control valve for openably/closably controlling the communication passage is disposed in the communication passage. The communication passage is composed of two first communication passages 030 for allowing high compression gas to flow from the combustion chamber 013 to the chamber portion 029, and one second communication passage 033 for allowing an air-fuel mixture to flow from the chamber portion 029 to the combustion chamber 013. The control valve is composed of two first control valves 038 provided in the first communication passages 030, and one second control valve 037 provided in the second communication passage 033.
The first control valves 038 open the first communication passages 030 nearly at a point of time when an exhaust opening is closed. The first control valves close the first communication passages 030 at a mid point in the compression stroke. The second control valve 037 opens the second communication passage 033 nearly at a point of time when a scavenging opening is closed and closes the second communication passage 033 before the first communication passages 030 are closed at the mid point in the compression stroke. Reference numeral 036 designates a rotary valve having, in the peripheral portion, cutouts functioning as the first control valves 038 and the second control valve 037. Reference numeral 031 designates an opening, on the combustion chamber side, of each of the first communication passages 030, i.e., high compression gas intake opening. 032 is an opening, on the chamber portion side, of each of the first communication passages 030. 034 is an air-fuel mixture supply opening, opened on the combustion chamber side, of the second communication passage 033. Furthermore, 035 is an opening, on the chamber portion side, of the second communication passage 033.
A pair of right and left fuel injectors 041 are mounted in the cylinder block 3 in such a manner as to be disposed on both sides of the chamber portion 029 in the lateral direction. Immediately before the second control valve 037 opens the second communication passage 033, fuel injected from the fuel injectors 041 is obliquely streamed, from below, in an air-fuel mixture forming space 044 (see FIG. 12) formed by the cutout functioning as the second control valve 037. To be more specific, the fuel is streamed at an approximately central portion of the second communication passage 033 (see FIG. 13).
The air-fuel mixture is formed as follows: namely, when the second control valve 037 opens the second communication passage 033 along with rotation of the rotary valve 036, high compression gas charged in the chamber portion 029 flows in the second communication passage 033 from the chamber side opening 035 of the second communication passage 033, to be mixed with standby fuel. The air-fuel mixture thus formed is then press-fed by high pressure in the chamber portion 029, to be injected from the air-fuel supply opening 034 into the combustion chamber 013.
The internal combustion engine of this type, at the initial state of scavenging, the scavenging is performed only by air, and therefore, fuel (rich air-fuel mixture) press-fed to the combustion chamber by means of the above means flows in the combustion chamber having been sufficiently scavenged with air, to thereby form an air-fuel mixture having a suitable concentration in the combustion chamber. The air-fuel mixture thus formed is desirably burned in the combustion chamber. As a result, the engine of this type is advantageous in attaining high level fuel consumption performance and high exhaust gas purifying performance.
According to the above-described background art internal combustion engine, fuel is injected from the fuel injectors 041 directly toward the air-fuel mixture forming space 044 formed by the cutout functioning as the second control valve 037, and the fuel injection begins immediately before the second control valve 037 opens the second communication passage 033. Accordingly, part of the stream of fuel strongly sprayed, from below, from the fuel injectors 041 to the rotary valve 036 may be often impinged on the bottom of the groove (cutout) of the rotary valve 036, to be splashed therefrom in the lateral direction, with a result that the splashed fuel may be often scattered in the chamber portion 029 to adhere on the inner wall of the chamber portion 029. The amount of fuel adhering on the inner wall of the chamber portion 029 causes an error to the weighed amount of fuel supplied from the fuel injectors 041. To cope with such an inconvenience, according to the background art internal combustion engine, it has been required to supply a larger amount of fuel, capable of compensating for the amount of fuel adhering on the inner wall of the chamber portion 029. An object of the present invention is to eliminate the scattering of fuel in the chamber portion 029 due to impingement of the stream of fuel on the rotary valve.
To solve the above problem, according to the present invention, there is provided a two-cycle internal combustion engine including a combustion chamber; a chamber portion adjacent to the combustion chamber; a communication passage between the combustion chamber and the chamber portion; and a control valve, provided in the communication passage, for opening the communication passage nearly at a point of time when a scavenging opening is closed and closing the communication passage at a mid point in the compression stroke, wherein an air-fuel mixture flows from the chamber portion side into the combustion chamber via the communication passage by operating the control valve. The above two-cycle internal combustion engine is characterized as follows:
(1) A portion, on the chamber portion side, of the communication passage is taken as a gas passage for communicating the control valve to the chamber portion, and a fuel injector for injecting fuel is provided at a mid point in the gas passage via a connection passage in such a manner as to be directed to the inner wall surface of the gas passage while being slightly tilted toward the control valve.
With this configuration, since fuel is injected toward the control valve but is not directly impinged on the control valve, it is possible to reduce the degree of scattering of the fuel on the chamber portion side due to splashing of the fuel from the control valve, and hence to obtain an air-fuel mixture having an accurate air-fuel ratio.
(2) In the two-cycle internal combustion engine described in the item (1), a fuel sump recess is provided in a cylinder block at a boundary between the control valve and the gas passage.
With this configuration, until the control valve is opened after fuel having been impinged on the inner wall of the gas passage reaches the position of the control valve in a state before being opened, the fuel is captured in the fuel sump recess (space), and consequently, it is possible to prevent splashing of the fuel from the control valve and hence to positively supply the fuel into the combustion chamber at the time of starting the opening of the control valve.
(3) In the two-cycle internal combustion engine described in the item (2), fuel is injected from the fuel injector into the fuel sump recess.
With this configuration, it is possible to more positively capture fuel in the recess, and hence to more effectively prevent splashing of fuel.
(4) In the two-cycle internal combustion engine described in the item (1) or (3), fuel is diffusely injected from the fuel injector so that the spray of fuel is not spread in the axial line direction of the gas passage but is spread in a fan-shape in the direction perpendicular to both the axial line of the gas passage and the axial line of the fuel injector.
With this configuration, it is possible to more positively spread fuel in the gas passage or in the fuel sump recess.
(5) In the two-cycle internal combustion engine described in the item (1) or (3), the fuel injector is disposed in such a manner that the tip of the fuel injector does not project in the gas passage.
With this configuration, it is possible to extend a spraying distance of fuel from the tip of the fuel injector to the inner wall of the gas passage, and to reduce the disturbance of the gas flow and hence to make the amount of fuel adhering and remaining on the inner wall of the gas passage as small as possible.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.